Sunscreen (I buy SPF 45 since it's the same price as SPF 30).
Nice clothes for formal night.
A big yes to the hand sanitizer.
A big yes to your medications.
We never found a need for an extension cord......but they would be handy IF you bring any type of electronic equipment since the plugs probably aren't in the area where you will need them. Some bring hair dryers, although there are 1500 watt hair dryers built in the bathroom. My DD has long, very very thick hair and found the hair dryer in the cabin almost too hot for her, but I guess some on this board must have monster hair dryers at home, because they find the hair dryer inadequate.